I have poor hot water preassure at all taps in my house. about 1/4 the preassure or less of the cold water. the tank is only a few years old. i have tried replacing the valve going to the HW tank, because it was very old and not quite functioning properly anymore. no help. i am get fairly good preassure at the drain for the HW tank, so i know there is preassure in it. any thoughts what to look at next?